U.S. Pat. Nos. 4,097,436 and 4,219,591 describe a saponified vinyl acetate-vinyl alkoxysilane polymer produced by contacting a solution of vinyl acetate-vinyl alkoxysilane copolymer with an alcoholic solution of an alkali metal hydroxide and recovering a precipitated product. Further described is a process for contacting an acidified solution of a vinyl acetate-vinyl alkoxysilane copolymer with a substrate to form a water insoluble film.
U.S. Pat. No. 4,425,403 describes a lens coating composition prepared by reacting an acid hydrolyzed silane coupling agent with an aqueous solution of polyvinyl alcohol (91 to 94% saponification) and silica gel.
U.S. Pat. No. 3,959,242 describes a silane grafted polyvinyl alcohol polymer prepared by stepwise reaction of polyvinyl alcohol (87-89% saponified) with a silane coupling agent in the presence of an acid catalyst. These graft polymers are suitable for a mold release surface for preparing cast articles.
U.S. Pat. No. 4,489,117 discloses a magnetic tape abrasion coating produced by coating a melt extruded polyethylene terephthalate film with an aqueous solution of a water soluble polymer such as polyvinyl alcohol and a silane coupling agent and heat stretching the film. A water soluble polymer with a molecular weight of 100,000 to 1,000,000 is preferred along with a dimethyoxysilane or trimethoxysilane.
Silane coupling agents were disclosed in U.S. Pat. No. 4,480,072 as a useful means to crosslink between organic and inorganic materials. A common feature of this and other references is crosslinking organic polyvinyl alcohol polymers and copolymers with an inorganic silane coupling agent without forming a new composition of matter containing nonhydrolyzable covalent bonds. Yet in spite of what was known in the art, it remained for the present invention to introduce a new class of water soluble silated polyvinyl alcohols and alkali salts useful for preparing water resistant films.